1. Field of the Invention
The present invention relates to a contents distribution technology and more particularly to a method of efficiently distributing large volume of contents such as video data in a wide area network and an apparatus implementing the method.
2. Description of the Related Art
As the method of efficiently distributing large volume of contents such as video data in a wide area network, a method called contents distribution has hitherto been known (for example, “Smart Contents Distribution Service”, [online], NTT communications, [searched on Feb. 12, 2003], Internet <URL: http://www.ntt.com/globalip/scd_en/>: this literature is herein incorporated by reference).
In this method, it is necessary to arrange a large number of copy servers in the wide area network. In the copy servers, copies of contents provided by a distribution server of a service provider are placed. In an actual contents distribution service, the service provider contracts with a provider (hereinafter, referred to as a “CDN provider”) which provides the copy servers and a network, thereby obtaining a license to use the copy servers.
First, a client computer (in a company) requests the distribution server to distribute contents. Upon accepting this request, the distribution server locates a copy server nearest to the client and redirects the request for distribution of the contents to the located copy server by rewriting an IP address in a packet of the request. The copy server accepts the request for the distribution and distributes the contents to the client computer in place of the distribution server.
By using this method, the copy server performs (as proxy) a part of processing of contents distribution which should be performed by the distribution server. Accordingly, a load on the distribution server can be reduced. Moreover, since the contents are distributed from the copy server near the client in the network, the network bandwidth necessary for the contents distribution can be saved.
In the conventional method, the client receives contents distributed from the copy server by using the same protocol (for example, an HTTP protocol, an RTSP protocol or the like) as in the case of receiving contents distributed from the distribution server. In this case, it is an essential condition that the distribution server and the copy server use the same server software. Accordingly, it was not easy to introduce a new service using server software other than the server software (for example, a WWW server, a video distribution server or the like) installed in the servers owned by the CDN provider. Specifically, in the conventional method, when the service provider intended to introduce a new service which required introduction of a new data send/receive protocol, it was required that server software based on the new data send/receive protocol be installed in each server of the CDN provider.
Moreover, in the conventional method, when a plurality of server software applications based on different types of data send/receive protocols were installed in the servers owned by the CDN provider, a mechanism was not provided in which the plurality of server software applications share a disk capacity provided by the CDN provider. Accordingly, there was a problem that costs of managing disk capacities used by the respective server software applications became large. For example, when the CDN provider intended to change part of the disk capacity for use of a WWW server into the disk capacity for use of a video distribution server because extra space was gained in the disk capacity for use of the WWW server, the setting of the disk capacity for each server software application needed to be manually changed.
Furthermore, in the conventional method, the client computer which is to request the distribution of contents first requests the distribution server to distribute the contents, and the distribution server locates the copy server nearest to the client and then redirects the contents distribution request to the copy server. Accordingly, when contents on which access requests were concentrated at a time were included in a service, there was a problem of overhead for the access requests in the server of the service provider which performed the centralized management of contents.